US2763795A

US2763795A - Ventilating apparatus for a motor

Info

Publication number: US2763795A
Application number: US256726A
Authority: US
Inventors: Jr Addison Ballard Bradley
Original assignee: BIRTMAN ELECTRIC CO
Current assignee: BIRTMAN ELECTRIC Co
Priority date: 1951-11-16
Filing date: 1951-11-16
Publication date: 1956-09-18
Anticipated expiration: 1973-09-18

Description

Sept. 18, 1956 A. B. BRADLEY, JR

VENTILATING APPARATUS FOR A MOTOR 5 Sheets-Sheet 1 Filed Nov 16, 1951 Sept. 18, 1956 A. B. BRADLEY, JR 2,763,795

7 VENTILATING APPARATUS FOR A MOTOR Filed Nov. 16. 1951 p 13, 1956 A. B. BRADLEY. JR

VENTILATING APPARATUS FOR A MOTOR 3 Sheets-Sheet 5 Filed Novv 16, 1951 //,;'IIIII United States Patent,

VENTILATING APPARATUS FOR A MOTOR Addison Ballard Bradley, Jr., Chicago, Ill., assignor to Birtman Electric Company, a corporation of Illinois Application November 16, 1951, Serial No. 256,726

2 Claims. (Cl. 310-62) This invention relates to a ventilating apparatus for a motor. Electric motors such as those used in vacuum cleaners and the like ordinarily develop considerable temperature rise especially during long periods of use. Because of the small space available, it has been ditficult to provide proper ventilation for the motor. Although centrifugal fans driven from the motor shaft have been proposed in the past, these fans have not always been eflicient because of eddy losses around the rotating blades that cut down on the amount of air circulated through the motor and because in most installations the air is merely recirculated within the motor.

In order to provide efiicient motor ventilation, I have provided a ventilating apparatus employing a centrifugal fan on the motor shaft that includes a plurality of circularly arranged blades together with a pair of guide means closely adjacent the sides of the blades to direct air outwardly therefrom in substantially streamline flow and thereby reduce eddy losses. The guide means between the fan and the motor is provided with an air inlet opening concentric with the fan and of considerably smaller diameter than the motor and adjacent to the inner edges of the blades of the fan. This baffie sets up streamline air flow and thereby causes a strong steady flow of cooling air across the motor and into the fan. In the preferred construction, this guide means is so shaped that it cooperates with the motor housing to provide a relatively unobstructed exit path for the ventilating air from the fan and cooperates with the motor .to direct the ventilating air across the motor in an 61116161112 manner and into the intake of the fan defined by the air inlet opening.

The invention will be described as shown in the accompanying drawings. Of the drawings: Fig. 1 is a fragmentary longitudinal vertical section through a vacuum cleaner embodying the invention; Fig. 2 is a front elevation of the rotatable impeller and associated structure; Fig. 3 is a fragmentary enlarged section taken substantially along line 3-3 of Fig. 2; Fig. 4 is a fragmentary enlarged elevational view showing the rotatable cutter blade approaching the fixed cutter blade; Fig. 5 is a section taken substantialy along line 5--5 of Fig. 1; and Fig. 6 is a rear elevational view of the motor casing and associated structure of the cleaner.

In the embodiment shown in the accompanying drawings the vacuum cleaner 10 is supported on spaced wheels 11 and is adapted to be propelled by means of a handle 12. The cleaner includes a casing 13 within an outer housing 14. The casing 13 is provided with a removable front portion 13a having roughly the shape of a truncated cone with the base portion arranged substantially vertically. The front portion 13a has an enlarged circular opening 13b at the front or apex thereof.

Spaced inwardly from the front portion 13a and substantially parallel thereto over a portion of its surface is a second casing portion 15 between the casing portions 13a and 15 there is located a centrifugal fan 16 of generally conical shape having a plurality of blades 17 there- 2,763,795 Patented Sept. 18, 1956 on. The blades are curved in the customary manner, as shown in Fig. 2, and extend slightly less than the full distance between the front casing portion 13a and the second casing portion 15.

The casing 13 rearwardly of the removable casing portion 13a is provided with an exhaust passage 18 of generally helical shape. As is shown in Fig. 5, this exhaust passage which is of expanding cross section communicates through almost 360 with the exhaust from the centrifugal impeller or fan 16. The entrance to the helical exhaust passage 18 is at the bottom of the cleaner in the area indicated at 19 in Fig. 5. The exhaust passage is of expanding cross sectional arear from the entrance 19 to the exit 21 which is adapted to be placed in communication with a dust bag in the usual manner.

It has been found in actual tests that the entrance 19 to the exhaust passage operates as a barrier against which pieces of paper and other foreign material tend to gather. If not removed, this paper and the like accumulates to such a large amount that it interferes with the efiicient operation of the cleaner. In order to remove this foreign material there is provided a fixed cutter blade 22 at- ICE,

tached as by screws 23 to the entrance 19 of the exhaust passage so that the cutting edge 22a extends beyond the casing at this entrance in position to have paper and other foreign material deposited thereon. This fixed blade has the cutting edge 22a concave with the point of deepest curvature being adjacent to the impeller 16.

Cooperating with the fixed cutter blade 22 is a second cutter blade 24 fastened to the impeller 16 for rotation therewith. In order to balance the impeller the portion thereof opposite the blade 24 is thickened as shown in Fig. 1 to provide a weighted portion substantially diametrically opposite the blade 24. The second cutter blade is provided with an inclined cutting edge adapted to cooperate with the cutting edge 22a of the fixed cutter blade 22 and sever paper and the like deposited thereon. As can be seen from Fig. 4, the concave cutter edge 22a and the sloped cutting edge 24a cooperate to have a slicing action or a scissors effect.

In order to rotate the fan or impeller 16, this impeller is mounted on a shaft 25 which serves as a part of the motor shaft 26. This shaft 25 extends through the opening 13b and is provided with a spindle 27 for driving a belt 28. This belt passes around the spindle 27 and then around the hub of a brush 29 for rotating this brush.

In the ordinary cleaner of the general type shown in the drawings it has been found that hair, string and the like work their Way in behind the impeller 16 and become wrapped around the rotating shaft 25 or around the inner surface of the hub of the impeller 16 through which the shaft 25 extends. In order to prevent this action there is provided a shield 30 attached to the casing that forms a part of the exhaust passage with this shield extending over the peripheral rim of the impeller 16 to prevent foreign material entering behind the impeller. In the embodiment shown in the drawings the shield includes an annular planar portion 30a extending outwardly from the inner wall 13d of the exhaust passage 18 and a cylindrical portion 30b overlapping the peripheral area or rim of the impeller 16. In the embodiment shown the casing portion 15 that is behind the impeller 16 is attached to the remainder of the casing in which the exhaust passage 18 is located by means of spaced bolts 31. The planar portion 30a of the shield is clamped between the casing portion 15 and the casing portion in which the exhaust passage 18 is formed.

In order to provide efiicient ventilation of the motor 32, there is provided a centrifugal ventilating fan 33 mounted on the motor shaft 26 immediately behind the front shaft bearing 34. Air is directed into the center of this fan 33 by means of a baffle 35 located inwardly of the fan 33 and the wall 13d defining the exhaust air passage 18 from the nozzle 20 of the cleaner. This baffle 35 has a substantially cylindrical portion 35a positioned inwardly of the wall 13d and a substantially annular planar portion 35b located at the inner end of the portion 35a. This planar portion 35b extends to the wall 13d to make an effective sealing contact therewith. On the front edge of the cylindrical portion 35a there is provided another planar portion 35c extending inwardly and located just rearwardly of the rear edges of the blades 33a of the fan 33. This planar portion 35c is provided with an air inlet opening 35d concentric with the fan 33. This circular opening 35d is located just outwardly of the innermost edges 33b of the fan blades 33a. With this construction, rotation of the fan 33 causes air to be drawn across the motor 32 and through the opening 35d in the other planar portion 35c and then forced outwardly by the rotating blades 33a into the passage 36 defined by the inner surface of the wall 13d, the cylindrical portion 35a and the first planar portion 3511.

In order to provide entrance and exhaust of the motor cooling air, the frame 37 containing the motor 32 is provided on its rear surface with air entrance openings 37a, 37b, 37c, 37d, and 37e. When the fan 33 is in operation, air is drawn through .these openings 37a to 37c, inclusive, where it flows across the motor 32v and through the shield opening 35d into the center of the centrifugal fan 33. From this fan, the air flows outwardly between guide means formed by the second casing portion 15 and bafile planar portion 350 and then through the passage 36. The air then passes out an opening 38 (Fig. to the atmosphere. This opening is formed by cutting away a portion of the casing 13d just to the rear of and upwardly from the exhaust passage entrance 19. This cut-out part forming the opening 38 extends arcuately around the fan 33 about 90 (Fig. 5) and is located to the right of the casing portion forming the exhaust air passage when the cleaner is viewed from the front of Fig. 1 and is also located in communication with the exhaust passage 36 defined by the bafiie 35.

The bafiie 35 and associated structure have a multiple function. In one respect, by locating the cylindrical portion 35a adjacent the motor 32 the shield serves to direct air across the motor for maximum cooling. Similarly, the inwardly directed planar portion 35c also aids in directing air across the motor. The combination of the portion 35a and the planar portions 35b and 350 also provide one side of the outlet passage 36 for exhausting the air from the centrifugal fan 33. By locating the guide means including the planar portion 35c adjacent to the blades 33a the fan 33 operates at maximum efiiciency to draw a strong air current across the motor in sub stantially streamline flow. By locating the inlet opening 350? in the baffle adjacent the inner edges of the blades 33a, all of the air is directed to the inner edges of the blades 33a so that maximum suction and thus maximum air flow is obtained. The baflie also has the feature of substantially reducing eddy currents and the entire structure prevents recirculation as ventilating air is drawn into the motor through the rear and exhausted out the side.

The thread shield including the member 30 and associated structure is described and claimed in Frank S. Howard application Serial No. 256,874, filed November 17, 1951. The cutter mechanism including the

blades

22 and 24 and associated structure is described and claimed in Charles H. Sparklin application Serial No. 256,701, filed November 16, 1951, now Patent No. 2,733,000.

Having described my invention as related to the embodiment shown in the accompanying drawings, it is my intention that the invention be not limited by any of the details of description unless otherwise specified but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

I claim:

1. An electric motor construction, comprising: a hollow casing; magnetic core members therein spaced from an end wall and from the side walls of the casing; a motor shaft; a centrifugal fan on the shaft between the magnetic core members and an end Wall; and a thin baffle around the end of the magnetic core members that is adjacent to the fan and spaced from the magnetic core members and the casing, the baflle including a first planar portion spaced from but between the fan and the adjacent end of the magnetic core members and including a ventilating opening spaced inwardly of the outer edges of the magnetic core members, a cylindrical portion on the periphery of the first planar portion extending rearwardly thereof, the cylindrical portion being spaced from the magnetic core members to direct ventilating air between this portion and the magnetic core members and thus across the magnetic core members, the cylindrical portion also being spaced from the casing to form an exhaust passage for the air, and a second planar portion extending outwardly from the rear end of the cylindrical portion toward the casing to complete said exhaust passage and to assist in directing air across the magnetic core members and into the fan.

2. The motor construction of claim 1 wherein said ventilating opening is substantially concentric with the fan and has its edge located adjacent to the inner edges of the fan blades.

References Cited in the file of this patent V UNITED STATES PATENTS 1,115,406 Davis Oct. 27, 1914 1,672,680 Freiburghouse June 5, 1928 1,920,309 Hoseason Aug. 1, 1933 FOREIGN PATENTS 119,726 Austria Nov. 10, 1930 229,946 Switzerland Mar. 1, 1944 482,136 Germany Sept. 7, 1929 716,297 France Oct. 6, 1931 a at